Hibernate快速入門

1.hibernate.cfg.xml Hibernate配置文件

<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- Database connection settings --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url"><!--[CDATA[ jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8]]--></property> <property name="connection.username">root</property> <property name="connection.password">hellopw</property> <!-- JDBC connection pool (use the built-in) --> <property name="connection.pool_size">100</property> <!-- SQL dialect --> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!--<property name="dialect">org.hibernate.dialect.HSQLDialect</property>--> <!-- Enable Hibernate's automatic session context management --> <property name="current_session_context_class">thread</property> <!-- Disable the second-level cache --> <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <!-- Echo all executed SQL to stdout --> <property name="show_sql">true</property> <!-- Drop and re-create the database schema on startup --> <property name="hbm2ddl.auto">create</property> <mapping resource="orm/hibernate/vo/User.hbm.xml"/> <mapping resource="orm/hibernate/vo/Address.hbm.xml"/> <mapping resource="orm/hibernate/vo/Message.hbm.xml"/> <mapping resource="orm/hibernate/vo/UserIdCard.hbm.xml"/> <!-- Annotation cfg --> <!--<mapping class="orm.hibernate.vo.User"/> <mapping class="orm.hibernate.vo.Address"/> <mapping class="orm.hibernate.vo.UserIdCard"/> <mapping class="orm.hibernate.vo.Message"/>--> </session-factory> </hibernate-configuration>

可以使用XML或者是annotation配置持久類.

 

2. 使用XML配置持久類mapping

(1) User.hdb.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="orm.hibernate.vo"> <class name="User" table="USER" lazy="true"> <id name="id" column="ID"> <generator class="uuid"></generator> </id> <property name="name" column="NAME" not-null="true" length="256" /> <set name="messages" table="USERMESSAGE"> <key column="USERID" /> <many-to-many column="MESSAGEID" class="Message" /> </set> <set name="addresses"> <key column="USERID" /> <one-to-many class="Address" /> </set> <one-to-one name="userIdCard" class="UserIdCard" /> <!--<many-to-one name="userIdCard" column="USERIDCARDID" unique="true" not-null="true"></many-to-one>--> </class> </hibernate-mapping>

(2)UserIdCard.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="orm.hibernate.vo"> <class name="UserIdCard" table="USERIDCARD"> <id name="id" column="USERIDCARDID"> <generator class="foreign"> <param name="property">user</param> </generator> </id> <property name="seqNumber" column="SEQNUMBER" not-null="true" length="128" /> <one-to-one name="user" class="User" constrained="true" /> <!--<id name="id" column="ID"> <generator class="uuid"></generator> </id> <property name="seqNumber" column="SEQNUMBER" not-null="true" length="128" /> <one-to-one name="user" property-ref="userIdCard" fetch="join"></one-to-one> --> </class> </hibernate-mapping>

(3) Address.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="orm.hibernate.vo"> <class name="Address" table="ADDRESS"> <id name="id" column="ID"> <generator class="uuid" /> </id> <property name="address" column="ADDRESS" length="512" /> <many-to-one name="user" column="USERID" /> </class> </hibernate-mapping>

(4) Message.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="orm.hibernate.vo"> <class name="Message" table="MESSAGE"> <id name="id"> <generator class="uuid"></generator> </id> <property name="content" column="CONTENT" not-null="true" /> <set name="users" table="USERMESSAGE" inverse="true"> <key column="MESSAGEID" /> <many-to-many column="USERID" class="User" /> </set> </class> </hibernate-mapping>

 

3. POJO

Address.java

package orm.hibernate.vo; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; import org.hibernate.annotations.GenericGenerator; @Entity @Table(name="ADDRESS") public class Address { @Id @Column(name="ID") @GeneratedValue(generator="system-uuid") @GenericGenerator(name="system-uuid", strategy="uuid") private String id = null; @Column(name="ADDRESS") private String address = null; @ManyToOne(fetch=FetchType.LAZY) @JoinColumn(name="USERID") private User user = null; /** * @return the user */ public User getUser() { return user; } /** * @param user the user to set */ public void setUser(User user) { this.user = user; } /** * @return the id */ public String getId() { return id; } /** * @param id the id to set */ public void setId(String id) { this.id = id; } /** * @return the address */ public String getAddress() { return address; } /** * @param address the address to set */ public void setAddress(String address) { this.address = address; } }

 

Message.java

package orm.hibernate.vo; import java.util.Set; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.ManyToMany; import javax.persistence.Table; import org.hibernate.annotations.GenericGenerator; @Entity @Table(name="MESSAGE") public class Message { @Id @Column(name="ID") @GeneratedValue(generator="system-uuid") @GenericGenerator(name="system-uuid", strategy="uuid") private String id = null; @Column(name="CONTENT") private String content = null; @ManyToMany(mappedBy="messages") private Set<User> users = null; /** * @return the id */ public String getId() { return id; } /** * @param id the id to set */ public void setId(String id) { this.id = id; } /** * @return the content */ public String getContent() { return content; } /** * @param content the content to set */ public void setContent(String content) { this.content = content; } /** * @return the users */ public Set<User> getUsers() { return users; } /** * @param users the users to set */ public void setUsers(Set<User> users) { this.users = users; } }

 

 

User.java

package orm.hibernate.vo; import java.util.Set; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.JoinTable; import javax.persistence.ManyToMany; import javax.persistence.OneToMany; import javax.persistence.OneToOne; import javax.persistence.PrimaryKeyJoinColumn; import javax.persistence.Table; import javax.persistence.Transient; import org.hibernate.annotations.GenericGenerator; @Entity @Table(name="USER") public class User { @Id @Column(name="ID") @GeneratedValue(generator="system-uuid") @GenericGenerator(name="system-uuid", strategy="uuid") private String id = null; @Column(name="NAME") private String name = null; @ManyToMany @JoinTable( name="USERMESSAGE", joinColumns={@JoinColumn(name="USERID")}, inverseJoinColumns={@JoinColumn(name="MESSAGEID")} ) private Set<Message> messages = null;//Many to many @OneToMany(mappedBy="user") private Set<Address> addresses = null;//One to many @OneToOne(fetch=FetchType.LAZY) @PrimaryKeyJoinColumn private UserIdCard userIdCard = null;//One to one /** * @return the userIdCard */ public UserIdCard getUserIdCard() { return userIdCard; } /** * @param userIdCard the userIdCard to set */ public void setUserIdCard(UserIdCard userIdCard) { this.userIdCard = userIdCard; } /** * @return the id */ public String getId() { return id; } /** * @param id the id to set */ public void setId(String id) { this.id = id; } /** * @return the name */ public String getName() { return name; } /** * @param name the name to set */ public void setName(String name) { this.name = name; } /** * @return the messages */ public Set<Message> getMessages() { return messages; } /** * @param messages the messages to set */ public void setMessages(Set<Message> messages) { this.messages = messages; } /** * @return the addresses */ public Set<Address> getAddresses() { return addresses; } /** * @param addresses the addresses to set */ public void setAddresses(Set<Address> addresses) { this.addresses = addresses; } }

 

UserIdCard.java

package orm.hibernate.vo; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToOne; import javax.persistence.Table; import org.hibernate.annotations.GenericGenerator; import org.hibernate.annotations.Parameter; @Entity @Table(name="USERIDCARD") public class UserIdCard { @Id @Column(name="USERIDCARDID") @GeneratedValue(generator="foreign") @GenericGenerator(name="foreign", strategy="foreign", parameters={@Parameter(name="property",value="user")}) private String id = null; @Column(name="SEQNUMBER") private String seqNumber = null; @OneToOne(mappedBy="userIdCard", fetch=FetchType.LAZY) private User user = null; /** * @return the user */ public User getUser() { return user; } /** * @param user the user to set */ public void setUser(User user) { this.user = user; } /** * @return the id */ public String getId() { return id; } /** * @param id the id to set */ public void setId(String id) { this.id = id; } /** * @return the seqNumber */ public String getSeqNumber() { return seqNumber; } /** * @param seqNumber the seqNumber to set */ public void setSeqNumber(String seqNumber) { this.seqNumber = seqNumber; } }

 

TestHibernate.java

package orm.hibernate.vo; import java.util.HashSet; import java.util.List; import java.util.Set; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.AnnotationConfiguration; import org.hibernate.cfg.Configuration; public class TestHibernate { private SessionFactory sessions = null; //new Configuration().configure("orm/hibernate/vo/hibernate.cfg.xml").buildSessionFactory(); private String userID = null; private String addressID = null; public TestHibernate(boolean annotationConfig) { this.sessions = annotationConfig ? new AnnotationConfiguration().configure("orm/hibernate/vo/hibernate.cfg.xml").buildSessionFactory() : new Configuration().configure("orm/hibernate/vo/hibernate.cfg.xml").buildSessionFactory(); } public void testAdd() { Session session = this.sessions.getCurrentSession(); session.beginTransaction(); //Save user User user = new User(); user.setName("AdersonJ"); session.save(user); //Save address Address address = new Address(); address.setAddress("Beijing city"); address.setUser(user); session.save(address); this.addressID = address.getId(); address = new Address(); address.setAddress("Shanghai city"); address.setUser(user); session.save(address); //Save message Message message = new Message(); message.setContent("The weather report for tomorrow."); session.save(message); // Set<User> users = new HashSet<User>(); // users.add(user); // message.setUsers(users); // session.update(message); Set<Message> messages = new HashSet<Message>(); messages.add(message); user.setMessages(messages); session.update(user); //Save userIdCard UserIdCard userIdCard = new UserIdCard(); userIdCard.setSeqNumber("ABCDEFG"); userIdCard.setUser(user); session.save(userIdCard); session.getTransaction().commit(); this.userID = user.getId(); } @SuppressWarnings("unchecked") public void testQuery() { Session session = this.sessions.getCurrentSession(); session.beginTransaction(); // List<Object> ls = (List) session.createQuery("from User user inner join user.userIdCard where user.name=?").setParameter(0, "AdersonJ").list(); // Object[] ary = (Object[]) ls.get(0); // User user = (User) ary[0]; // List ls = session.createQuery("from User user where user.name=?").setParameter(0, "AdersonJ").list(); // User user = (User) ls.get(0); // System.out.println(user.getName()); // User user = (User) session.load(User.class, this.userID); // System.out.println(user.getName()); //Address address = (Address) session.createQuery("from Address as address where address.address=?").setParameter(0, "Beijing city").uniqueResult(); Address address = (Address) session.load(Address.class, this.addressID); System.out.println(address.getAddress()); session.getTransaction().commit(); } ///////////////////////////////////////////////////////////////// public void testAnnotationAdd() { Session session = this.sessions.getCurrentSession(); session.beginTransaction(); //Save user User user = new User(); user.setName("AdersonJ"); session.save(user); //Save address Address address = new Address(); address.setAddress("Beijing city"); address.setUser(user); session.save(address); this.addressID = address.getId(); address = new Address(); address.setAddress("Shanghai city"); address.setUser(user); session.save(address); //Save message Message message = new Message(); message.setContent("The weather report for tomorrow."); session.save(message); // Set<User> users = new HashSet<User>(); // users.add(user); // message.setUsers(users); // session.update(message); Set<Message> messages = new HashSet<Message>(); messages.add(message); user.setMessages(messages); session.update(user); //Save userIdCard UserIdCard userIdCard = new UserIdCard(); userIdCard.setSeqNumber("ABCDEFG"); userIdCard.setUser(user); session.save(userIdCard); session.getTransaction().commit(); this.userID = user.getId(); } public void testAnnotationQuery() { Session session = this.sessions.getCurrentSession(); session.beginTransaction(); // User user = (User) session.load(User.class, this.userID); // System.out.println(user.getName()); // User user = (User) session.createQuery("from User user where user.name=?").setParameter(0, "AdersonJ").uniqueResult(); // System.out.println(user.getUserIdCard()); Address address = (Address) session.load(Address.class, this.addressID); System.out.println(address.getAddress()); session.getTransaction().commit(); } public static void main(String[] args) throws Exception { TestHibernate test = new TestHibernate(false); test.testAdd(); test.testQuery(); //Thread.sleep(200000); // test.testAnnotationAdd(); // test.testAnnotationQuery(); } }

 

4. 注意事項.

(1) User <-> UserIdCard 是OneToOne, XML配置lazy沒有lazy="true", annotation雖然fetch=FetchType.LAZY, 其實不生效的, load User對象的時候一般hibernate會主動load UserIdCard對象, 使用left outter join.

這裏使用的是公用主鍵, 使用外鍵配置文檔有例子（XML註釋部分）。

注意使用User user = (user) session.createQuery().uniqueResult(); 和session.load(User.class, "userIDxxx");生成的SQL, 注意調優, fetch join, outter join等. 

Annotation配置的UserIdCard.user不寫lazy的話, load User by ID 默認會User left join UserIdCard left join User, 有點奇怪?

 

(2) User <-> Address OneToMany and ManyToOne,  XML配<many-to-one lazy沒有true, 不配置lazy, load Address的時候不會去load User, annotation配置@ManyToOne的時候不加lazy的話會自動load User, 有點不一樣.

 

(3)<many-to-many> 和@ManyToMany就inverse="true"的一方不去維護關聯表UserMessage更新, 在這裏User.setMessages()之後session會更新UserMessage表, 但是Message.setUser()後不會更新. 雙向的關聯時候爲了避免一些表的鍵的衝突, 甚至是減少生成的SQL.

 

(4) Hibernate entity/annotation reference和hibernate reference有關於mapping的更詳細全面配置說明.

(5) 這裏都是雙向關聯, 根據應用設置關聯, lazy, fetch 方式.

(6) Hibernate是持久層的一種選擇方案, 符合關係型數據庫設計準則, 穩定成熟的一個方案, 能夠較好解決大多數問題 但是它存在緩存, 對於多個應用更新採訪同一服務器， 或者是 以爲數據庫爲中心的業務開發(使用存儲過程等) 應注意緩存屏蔽; 動態表,  對於現有一些系統(使用JDBC等)升級, 要謹慎設置使用.